<template>
  <el-color-picker v-model="theme" class="theme-picker" popper-class="theme-picker-dropdown" />
</template>

<script>
const version = require('element-ui/package.json').version // element-ui version from node_modules
const ORIGINAL_THEME = '#0A9690' // default color

export default {
  data() {
    return {
      chalk: '', // content of theme-chalk css
      theme: ORIGINAL_THEME,
    }
  },

  watch: {
    theme: {
      handler(val, oldVal = '#409EFF') {
        console.log(val, oldVal)
        if (typeof val !== 'string') return
        const themeCluster = this.getThemeCluster(val.replace('#', ''))
        const originalCluster = this.getThemeCluster(oldVal.replace('#', ''))
        const getHandler = (variable, id) => {
          return () => {
            // const originalCluster = this.getThemeCluster(ORIGINAL_THEME.replace('#', ''))
            const newStyle = this.updateStyle(this[variable], originalCluster, themeCluster)

            let styleTag = document.getElementById(id)
            if (!styleTag) {
              styleTag = document.createElement('style')
              styleTag.setAttribute('id', id)
              document.head.appendChild(styleTag)
            }
            styleTag.innerText = newStyle
          }
        }

        const chalkHandler = getHandler('chalk', 'chalk-style')
        if (!this.chalk) {
          // const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`
          // let element = document.querySelector('link[rel^="stylesheet"]')
          const links = document.querySelectorAll('link')
          let strLink = []
          let str = ''
          ;[...links]
            .filter((v) => v['href'].endsWith('.css'))
            .forEach((v) => {
              strLink.push(this.varmyNewAjax(v.href))
            })
          if (strLink.length) {
            // const url = element.getAttribute('href')
            // this.getCSSString(url, chalkHandler, 'chalk')
            Promise.all(strLink)
              .then((result) => {
                str = result.join(' ')
                this.chalk = str.replace(/@font-face{[^}]+}/, '')
                chalkHandler()
              })
              .catch((error) => {
                console.log(error)
              })
          }
        }
        const styles = [].slice.call(document.querySelectorAll('style')).filter((style) => {
          const text = style.innerText
          return new RegExp(oldVal, 'i').test(text) && !/Chalk Variables/.test(text)
        })
        styles.forEach((style) => {
          const { innerText } = style
          if (typeof innerText !== 'string') return
          style.innerText = this.updateStyle(innerText, originalCluster, themeCluster)
        })
        if (val?.toUpperCase() === this.theme && oldVal?.toUpperCase() === '#409EFF') {
          return
        }
        this.$message({
          message: '换肤成功',
          type: 'success',
        })
      },
      immediate: true,
    },
  },
  methods: {
    updateStyle(style, oldCluster, newCluster) {
      let newStyle = style
      oldCluster.forEach((color, index) => {
        newStyle = newStyle.replace(new RegExp(color, 'ig'), newCluster[index])
      })
      return newStyle
    },

    getCSSString(url, callback, variable) {
      const xhr = new XMLHttpRequest()
      xhr.onreadystatechange = () => {
        if (xhr.readyState === 4 && xhr.status === 200) {
          this[variable] = xhr.responseText.replace(/@font-face{[^}]+}/, '')
          callback()
        }
      }
      xhr.open('GET', url)
      xhr.send()
    },

    getThemeCluster(theme) {
      const tintColor = (color, tint) => {
        let red = parseInt(color.slice(0, 2), 16)
        let green = parseInt(color.slice(2, 4), 16)
        let blue = parseInt(color.slice(4, 6), 16)

        if (tint === 0) {
          // when primary color is in its rgb space
          return [red, green, blue].join(',')
        } else {
          red += Math.round(tint * (255 - red))
          green += Math.round(tint * (255 - green))
          blue += Math.round(tint * (255 - blue))

          red = red.toString(16)
          green = green.toString(16)
          blue = blue.toString(16)

          return `#${red}${green}${blue}`
        }
      }

      const shadeColor = (color, shade) => {
        let red = parseInt(color.slice(0, 2), 16)
        let green = parseInt(color.slice(2, 4), 16)
        let blue = parseInt(color.slice(4, 6), 16)

        red = Math.round((1 - shade) * red)
        green = Math.round((1 - shade) * green)
        blue = Math.round((1 - shade) * blue)

        red = red.toString(16)
        green = green.toString(16)
        blue = blue.toString(16)

        return `#${red}${green}${blue}`
      }

      const clusters = [theme]
      for (let i = 0; i <= 9; i++) {
        clusters.push(tintColor(theme, Number((i / 10).toFixed(2))))
      }
      clusters.push(shadeColor(theme, 0.1))
      return clusters
    },

    varmyNewAjax(url) {
      return new Promise(function (resolve, reject) {
        var xhr = new XMLHttpRequest()
        xhr.open('get', url)
        xhr.send()
        xhr.onreadystatechange = function () {
          if (xhr.status == 200 && xhr.readyState == 4) {
            resolve(xhr.responseText)
          } else if (xhr.readyState == 4 && xhr.status != 200) {
            reject('error')
          }
        }
      })
    },
  },
}
</script>

<style>
.theme-picker .el-color-picker__trigger {
  vertical-align: middle;
}

.theme-picker-dropdown .el-color-dropdown__link-btn {
  display: none;
}
</style>
